The Trades of Tin Plate and Wire Working
The trades of tin plate working and wire drawing continue to this day to make an important
contribution to our everyday lives, to industry and to the economy. This paper, produced by the Worshipful Company of Tin Plate Workers alias Wire Workers, offers a short introduction:
The trade of tinplate making covers both the manufacture of tinplate from steel and the conversion of this into metal packaging, widely used for food and beverage cans and other
products. Tin coating on thinly rolled sheet steel provides resistance to corrosion. It is used both to protect food, beverage or other products contained in the package (the ‘can’ or ‘tin’) and to resist external factors such as heat processing steam/water systems. A polymer coating is sometimes added on the inside surface, to prevent chemical action and the possible transfer of taint between metal and product.
Tinplate has been commercially made in the UK since the late 1600s, originally by dipping sheets of wrought iron, and later steel, into baths of molten tin. During WWII, electro-coating (or electroplating) was introduced, allowing the continuous application of tin to both sides of the metal simultaneously; tin could thus be applied to wide coils of steel, which could be unwound, coated and then rewound. This, in turn, encouraged the concentration of manufacture onto fewer sites.A hundred years ago there were 83 tinplate works, mostly in South Wales. Today, there is a single UK manufacturer, Tata Packaging Steel at the Trostre factory in Llanelli, though many businesses make packaging products.
Tinplate products include processed food and drinks cans; aerosols; lug caps (for glass jars); crown caps (for drink bottles); and homecare, DIY (eg. paint), industrial, promotion and giftware containers. Tinplate is inherently stronger than aluminium, so it is used both for seamless thin wall cans and for cans made by rolling flat sheets and welding or folding a side seam. By contrast, aluminium is generally only used for containers that have internal pressure after filling, or where the strength of the side wall is not critical. Thus aluminium is used for seamless thin wall cans for beer and carbonated soft drinks; aerosols made by impact extrusion; seamless shallow fish (eg. sardine) and other food cans; and most caps and closures other than those listed above for tinplate. In Europe, around 80% of seamless beverage cans are made from aluminium and 20% from tin plate.Today, some 23 UK metal packaging businesses employ approximately 4,200 employees, in 32 factories, using around 665,000 tonnes of metal annually. In Europe as a whole:
- there are over 200 companies, 70,000 employees and 300 factories;
- five million tonnes of metal makes over 70 billion metal packaging units every year;
(worldwide estimate: 400 billion metal packaging units and 300 billion crown caps) metal packaging comprises 15% of the European packaging industry by turnover.
For more information on the history of the Company and its trades, see: Oliver Warne, A History of the Company of Tin Plate Workers alias Wire Workers, (2nd edn. ed. Andrew Hill), Jeremy Mills Publishing, 2009.
- Electro chrome coated steel (also known as tin free steel) is a slightly cheaper alternative, but always requires a sealing coat of organic material to provide a complete protection system.
- Aluminium does not require metallic coatings, but all surfaces must be chemically cleaned and coated with organic material to prevent chemical action from the product or external environment.
- Sources: Metal Packaging Manufacturers’ Association (UK) and European Metal Packaging (Brussels).
Wire drawing involves mechanically pulling metal rods through a series of progressively smaller dies, a process known as ‘cold drawing’. Wire has many thousands of uses, from cables and ropes for bridges, mining and fishing, to piano wire; from supermarket trolleys to medical instruments; from telecommunications and power cables to fencing; Cold drawing reduces the diameter and changes the properties of the metal; it can be repeated several times, and the wire may be heat treated between passes to counteract hardening and restore ductility. Wire is usually circular, but it can be made with any section by varying the die holes. It can also be galvanized and/or coated to provide corrosion protection. Steel, copper, aluminium and nickel are used to make wire, the choice depending on its use. Dies are made from tungsten carbide or diamond.
Precious metals have been used to make wire for jewellery since antiquity. The Egyptians were drawing strips of metal through stone beads by the 2nd dynasty, and a swaging technique (a metal rod struck between grooved metal blocks) may have been used in Bronze and Iron Age Europe. Wire has been drawn in England since mediaeval times, to make wool cards and pins, and manufactured products such as hooks, cages, chains and traps. In 1568 Elizabeth I, keen to reduce English dependence on foreign goods, granted a patent to William Humfrey who, with William Cecil, had set up the first British wireworks in Tintern, Monmouthshire. They made iron and possibly brass wire, for use in the wool industry, and for nails, pins, knitting needles and fish hooks. Later, the invention of the ‘wortle plate’ introduced the drawing of wire through a perforated metal plate; the holes were punched into the plate at a forge and they could be heat treated and re-sized when they became worn.
The Victorians invented high tensile steel wire. In 1852, James Horsfall patented an isothermal lead bath quenching process that strengthened wire for producing needles, fish hooks and umbrella frames; with this process, he captured the whole global supply of piano wire. In 1866, with Joseph Webster, Horsfall manufactured 30,000 miles of armoured wire for the first transatlantic telegraph cable. Today there are:
- some 15 ferrous (iron and steel) wire drawing and cable making sites in the UK.
- they produce around 250,000 tonnes of wire every year.
- about 170,000 tonnes is exported, to other European countries and beyond.
Recycling and sustainability
Tinplate and wire are almost endlessly recyclable, and the raw materials that make them nearly always include recycled materials. Metal is the world’s most recyclable material – it can be melted down time and time again, to make new supplies of high quality metal. The UK metal recycling industry recovers up to 15 million tones of ‘scrap’ metal every year, supplies UK steelworks and foundries, and exports to almost every corner of the world.
Metal is also at the centre of Europe’s drive for sustainability and reduced dependence on virgin raw materials. European targets have been set for the reuse, recycling or other recovery of common products, which include:
- packaging : some 2 billion metal cans are recycled in the UK each year.
- waste electronic and electrical equipment : metals, including wire, make up 70% of white goods and 47% of small items, such as mobile phones.
- end of life vehicles : 75% of a car is metal, including wire used in fastenings, electrical connections and tyres. Around 2.2 million cars are recovered in the UK every year.
- Source: EEF, UK Steel Division
- Source: British Metals Recycling Association